Why Does Food Taste Bland When You Have a Cold?

Food tastes bland when you have a cold because most of what you think of as flavour is actually smell, and a blocked nose stops aroma molecules from reaching your smell receptors. Your tongue still detects the five basic tastes, sweet, salty, sour, bitter and umami, but without aroma, coffee, strawberries and roast chicken lose almost everything that makes them distinct. The good news is that taste, texture, temperature and spicy heat all still get through.

What's the difference between taste and flavour?

In everyday speech we use "taste" for the whole experience of eating. Scientists split it up.

Taste is what your tongue does. Taste buds detect five basic qualities: sweet, salty, sour, bitter and umami. (There's growing evidence for a sixth related to fat, but it's still debated.) That's a short list. Your tongue alone can tell a strawberry is sweet and a bit sour, but it can't tell a strawberry from a raspberry.

Flavour is taste plus smell, plus texture, temperature and sensations like the burn of chilli or the cool of mint, all blended by your brain into one impression. Smell does the heavy lifting. Humans have around 400 kinds of working smell receptors, and in combination they can distinguish an enormous number of aromas, compared with just five basic tastes.

You'll often read that "80% of flavour is smell". It's a catchy number, but it doesn't come from any solid study, and the real share varies from food to food. A spoonful of sugar is nearly all taste; a sip of coffee is nearly all aroma. The broad point holds, though: identifying most foods depends heavily on your nose.

How can you smell food that's already in your mouth?

There are two routes to your smell receptors, and the second one is the one most people don't know about.

1. Orthonasal smell is sniffing through your nostrils, like smelling bread baking from across the room.
2. Retronasal smell happens from the inside. As you chew and swallow, aroma molecules released from the food drift up the back of your throat into your nasal cavity, pushed along each time you breathe out.

Your smell receptors sit on a small patch of tissue, roughly the size of a postage stamp, high up inside your nose. Both routes have to reach that patch. Retronasal smell is so smoothly blended with taste that your brain files it under "mouth", which is why you feel like you're tasting flavours that you're really smelling.

Chef Fizz says: Your nose is the secret co-chef in every bite. When it calls in sick, the kitchen gets very quiet.

What does a cold actually do to your sense of smell?

A cold hits your sense of smell in two ways.

It blocks the airway. Viral infection makes the lining of your nose swell and produce lots of mucus. Air, and the aroma molecules riding on it, can't get up to the smell receptors through either route. This is the main reason for flat-tasting food during a cold, and it reverses as soon as the swelling goes down. You'll notice flavour flickering back when you briefly breathe more freely, such as after a hot shower.

It can irritate the smell tissue itself. Some viruses inflame or temporarily damage the smell receptors and the support cells around them. In that case, smell may stay weak for a while even after your nose feels clear. The smell system can regrow, and most people recover over weeks to months. COVID-19 made this kind of smell loss famous, but ordinary cold viruses can do it too.

Taste buds are rarely the problem. They keep working through most colds, so salty still tastes salty and sweet still tastes sweet. That's why sick people often say food tastes "like cardboard" rather than "like nothing at all". The basic tastes are still there; the personality is missing.

If your sense of smell hasn't returned a few weeks after a cold clears, or if you lose it suddenly without a blocked nose, it's worth talking to a doctor.

Why can you still feel chilli and mint?

Because they don't use smell or taste. Chilli heat, mint's coolness, mustard's sinus blast and the fizz of a soda travel through a separate set of nerves, mainly the trigeminal nerve, which senses touch, temperature and pain in your face, mouth and nose. Scientists call this chemesthesis.

• Chilli activates TRPV1, a heat-pain receptor. More in why chilli peppers burn.
• Mint contains menthol, which triggers the cold receptor TRPM8.
• Mustard, wasabi and horseradish trigger TRPA1, a receptor for irritants.
• Black pepper and ginger create warm, tingling heat.
• Carbonation forms carbonic acid in your mouth, which prickles pain nerves and sour taste cells.

None of these need a clear nose, so they cut through a cold. That's probably one reason spicy noodle soups and ginger tea feel so satisfying when you're sick: they deliver strong sensation when most of flavour has gone quiet.

Does temperature change how food tastes?

Yes, and it matters more when you're relying on taste alone.

Warmth boosts sweetness. The taste cells for sweet, bitter and umami share an ion channel called TRPM5, which becomes more active as temperature rises. That's why melted ice cream tastes sickly sweet while frozen ice cream tastes just right, and why a warm soft drink tastes syrupy.

Cold mutes taste. Very cold food and drinks taste less sweet and less intense overall. Your tongue is also slightly numbed by cold.

Heat releases more aroma. Warm food gives off far more volatile aroma molecules than cold food. If your nose is only partly blocked, a hot bowl of soup gives your smell receptors more to work with than a cold sandwich, and the steam may help open your nose for a moment.

Saltiness is less affected by temperature than sweetness, but a cold soup still tends to need more seasoning than the same soup served hot.

Want to explore how your senses build flavour? The Cooking Scientist app has quick lessons on why smell is flavour and how temperature changes taste, each with a mini game.

What should you cook when you can't taste anything?

When aroma is off the table, build food around everything else: the five tastes, physical sensations, texture and temperature.

• Lean on salt and umami. A well-seasoned broth with soy sauce, miso, parmesan or a dash of fish sauce delivers strong savoury taste straight to your tongue. See what is umami.
• Add acid. Lemon, lime or a splash of vinegar adds sourness, which you can still taste clearly, and makes food feel livelier. More in why acid brightens food.
• Bring the heat. Fresh ginger, chilli, black pepper and horseradish stimulate nerves that a cold doesn't touch.
• Play with texture. Crunchy toast, crisp vegetables or a fizzy drink give your mouth something to notice.
• Serve it hot. Warm food releases more aroma, boosts sweetness and feels comforting.

One warning for the cook: when your own smell is blunted, you may season food much more heavily than usual to make it taste of anything. If you're cooking for others while sick, measure the salt or ask someone else to taste.

Try it at home

The jelly bean nose-pinch test takes one minute and shows how much of flavour comes from your nose. You'll need a few jelly beans or fruit gummies in different flavours, and ideally a helper.

1. Close your eyes and have your helper hand you a jelly bean without telling you the flavour.
2. Pinch your nose firmly shut and chew. Notice what you can detect: probably sweet, maybe a little sour.
3. Keep chewing, then let go of your nose.

Within a second or two, the flavour floods in: cherry, lemon, green apple. Nothing changed in your mouth. You simply reopened the retronasal route, and aroma molecules rushed up to your smell receptors.

Try it with a pinch of cinnamon on a spoonful of sugar too. With your nose pinched it tastes like plain sugar with grit. Release, and it's suddenly cinnamon. That's exactly what a cold does to every meal, all day long.

Common mistakes

• Assuming your taste buds are broken. They're almost always fine during a cold. Food lacks aroma, not taste, so focus on the basic tastes and sensations.
• Over-salting while sick. Without aroma, food can taste dull no matter how much salt you add. Season by measuring rather than tasting, and let others adjust their own plates.
• Relying on delicate herbs and spices. Fresh basil, saffron or a subtle spice blend mostly reach you through smell and will barely register. Use ginger, chilli, citrus and umami instead.
• Eating everything cold. Chilled food releases less aroma and tastes less sweet. Warm meals give a partly blocked nose the best chance.
• Ignoring smell loss that lingers. Most colds clear and smell returns within days or weeks. If it doesn't come back a few weeks after you recover, see a doctor, because smell training and treatment can help.